1. Field of the Invention
The present invention relates in general to an adjustable bolt wrench and, in particular, to an adjustable, three-jawed wrench which can be adjusted for any size hexagonal bolt.
2. Description of the Prior Art
Bolt wrenches are an old art. There are primarily three general types of wrenches: socket wrenches, fixed end wrenches, and adjustable wrenches. In each type of wrench, there are several common ideal features. The wrench should be easy to use, since one-handed applications may be necessary in practice. Second, the head of the wrench, the section of the wrench that actually grips a bolt, must be able to grip the bolt in such a way that the corners of the standard hexagonal bolts are not stripped. Once stripped, the bolts become very difficult if not impossible to work with, and must be mechanically cut and replaced. The wrench should be simple in design and economical to manufacture.
Of the three basic types of wrenches in current use, adjustable wrenches offer the most versatility. Further, adjustable wrenches are easier to use than socket or fixed end wrenches, both of which require the user to either replace the socket for different applications or change out the entire wrench. This is time consuming and tedious in many working conditions. An adjustable wrench allows the user to adjust a single tool unit to the various shapes and sizes of bolts, both metric and standard.
The only drawback to adjustable wrenches is their gripping ability. Specifically, adjustable wrenches currently available are not able to fit a bolt as snugly as socket of fixed end wrenches. This often leads to stripping of the bolt head, which further complicates the loosening or tightening of a bolt. Generally, the advantage that socket and fixed end wrenches have in this regard is an increased contact area with the bolt head. Socket and fixed end wrenches are typically designed to contact each of the six corners of the bolt head as well as each side. The greater the contact area, the tighter the fit between the wrench and bolt. Thus, what is needed is a wrench that has the versatility of an adjustable wrench, but also the advantages of fixed and socket wrenches.
Most adjustable wrenches have two bolt claws that are adjustable relative to each other to contact the bolt head, typically on two opposing sides of the hexagonal bolt. Increasing the number of sides contacted, and the number of corners contacted would be ideal. This could be accomplished by increasing the number of bolt claws on the adjustable wrench, thus increasing the surface area of the bolt head contacted. There are pliers in the art that have such a feature. For instance, the Stallings (U.S. Pat. Nos. 1,250,690 and 1,498,488) inventions are pliers with two opposing claws, with a third pivotally mounted claw located central to the other two. The claw contact region is a complex structure, and the use of these pliers is directed towards general gripping of rounded surfaces such as pipes. These devices would not be suitable for a bolt wrench.
There are several other inventions directed towards an adjustable wrench. The Whelan (U.S. Pat. No. 1,401,931) invention is an adjustable pipe wrench that uses two opposing complex surfaced claws for gripping a pipe, with a third attachment coupled in such a manner to allow both parts to slide and pivot, increasing the contact surface area of the pipe being gripped. The Wei (U.S. Pat. No. 5,542,319) invention is an adjustable bolt wrench using two opposing bolt claws with a ratcheted handle. Although an improvement on the prior art, these two devices are either not directed towards a bolt wrench, or do not incorporate the advantages of fixed end wrenches by increasing the contact area of the bolt head and wrench. Thus, there is a need for a wrench that incorporates the ease of use of an adjustable wrench with the advantages of fixed end and socket wrenches.
U.S. Pat. No. 6,205,892, issued Mar. 27, 2001, to the present inventor was an improvement in providing a wrench with increased surface contact between the wrench head and the bolt being gripped. The present invention is directed toward further improvements in that basic design.